1. Field of the Invention
This invention relates to pretreatment agents to be used before bleaching or dyeing horny fibers such as the hair or idle hair, more particularly, a hair-treatment composition capable of supplying ferrous ions in a stable state to the horny fibers under weakly acidic mild conditions; a bleaching composition whereby the horny fibers such as the hair or idle hair can be bleached without giving much damage thereto under weakly acidic mild conditions while scarcely irritating, for example, the skin during the bleaching process; and a hair color tone modifier composition (hair dyeing composition) obtained by adding a hair dye to said bleaching composition.
2. Description of the Prior Art
Known bleaching agents for horny fibers such as the hair or idle hair contain hydrogen peroxide as an essential factor of their constituents. In most cases, this hydrogen peroxide, including perborates and percarbonates capable of liberating hydrogen peroxide at the application, would exert a bleaching effect in an aqueous state so as to oxidize and bleach melanin contained in the horny fibers such as the hair or idle hair. Such a bleaching agent is generally applied in the form of an alkaline aqueous solution (pH 8 to 11) in order to fully achieve the bleaching effect of the hydrogen peroxide. However there is a problem that hydrogen peroxide contained in an alkaline aqueous composition is unstable, which makes it difficult to store such a composition for a prolonged period of time.
Thus a bleaching agent containing hydrogen peroxide is frequently supplied in the form of a one-pack powdery bleaching agent, which is to be dissolved so as to give an alkaline aqueous solution at the application, or a two-pack bleaching agent) wherein a powdery or aqueous alkaline agent composition is to be mixed with a water-soluble hydrogen peroxide composition immediately before the application. In order to fully achieve the bleaching effect of these powdery one-pack and two-pack bleaching agents, it is required to elevate the pH value within an alkaline region or to increase the hydrogen peroxide content at the application. However these treatments, namely, the elevated pH value or increased hydrogen peroxide content would irritate the skin and mucosae so as to damage fibers including the hair.
Thus a pretreatment with ferrous ions has been conducted before bleaching or dyeing horny fibers such as the hair or idle hair in order to minimize the damage to the hair or improve the bleaching or dyeing effect.
For example, U.S. Pat. No. 3,632,295 discloses a two-stage method for bleaching the hair comprising applying the primary agent containing a ferrous salt to the hair and then applying an alkaline aqueous solution of hydrogen peroxide (of pH 8 to 11) to the hair as the secondary agent; Japanese Patent Publication No. 37004/1987 discloses a three-pack bleaching agent which consists of the primary agent containing a sulfite, the secondary agent containing a ferrous salt and the tertiary agent containing unstable hydrogen peroxide; and Japanese Patent Publication No. 55483/1986 discloses a two-pack hair dye consisting of the primary agent in the form of a commonly used hair tonic containing a ferrous salt and the secondary agent which is in the form of a hair conditioner containing a color former and may be used at an appropriate stage thereafter.
Furthermore, West German Patent No. 3,149,978 discloses a method comprising applying a ferrous compound as a reducing agent together with phosphorous acid to keratin fibers and then bleaching the keratin fibers with hydrogen peroxide.
An aqueous solution of a ferrous salt to be used as a pretreatment agent suffers from some troubles such that it would form hardly soluble ferrous hydroxide at a pH value of 5 or higher and that it would irritate the skin or mucosae at a pH value of 3.0 or lower. In order to stably and safely penetrate a ferrous salt into the hair, therefore, it has been attempted to control the pH value by using an ferrous salt solution as a buffer system. However there are still some problems in this method. Among organic acids commonly used in a buffer system, acetic acid has a characteristic odor while citric acid would cause the coloration of a chelate compound thereof with the ferrous ion.
When an alkaline aqueous solution of hydrogen peroxide is to be used as a bleaching agent, as in the case of the above-mentioned method of the U.S. Pat. No. 3,632,295, the hydrogen peroxide in said alkaline aqueous solution of hydrogen peroxide is unstable. Thus it is difficult to provide a stable aqueous composition available in practice unless the product is formulated into a three-pack composition wherein an alkali composition (the secondary agent) is mixed with a water-soluble hydrogen peroxide composition (the tertiary agent) immediately before the application.
On the other hand, the above-mentioned three-pack bleaching agent of the Japanese Patent Publication no. 37004/1987 cannot always be convenient, since it requires a complicated bleaching procedure and a long treatment period.
In the case of the above-mentioned bleaching method described in the West German Patent No. 3,149,978, furthermore, sufficient care should be taken in the pretreatment conducted under strongly acidic conditions and in the rinsing with an acidic solution such as phosphoric acid for removing the remaining phosphorous acid. Further, this product would sometimes cause significant irritation on the skin and mucosae when applied to the body.
When a hydrogen peroxide solution alone is to be used within a weakly acidic or neutral region, a satisfactory bleaching effect can be scarcely achieved. When the hydrogen peroxide concentration is increased or the solution is repeatedly used in order to enhance the bleaching effect, .fibers including the hair would be frequently damaged.